How are you activating the function, hotkey combo or menu?If no improvement using Safe Mode, do you have the same problem if you create a new profile and test it with no extensions or non-default themes installed?http://kb.mozillazine.org/Profile_Manager

Problem solved.Dan, you were on the right track, as was Ed Mullen who was a big help.One of the profile bookmark-related files was apparently corrupted. Before setting up a new profile, I decided to try copying the bookmark, ab, places files from another SM computer, and that fixed the problem.Thanks again, everyone.